CELTIC last night blamed Hammarby supporters for the crowd trouble that broke out in the stands during their Europa League play-off against AIK in the Friends Arena in Stockholm.

Flares were set off in the away section after the second leg match kicked off and stewards wearing hard hats had to go in to extinguish one of the pyrotechnics with sand.

At half-time there were violent skirmishes between Swedish police and supporters in the same area of the stadium with punches being thrown and batons being used.

The Scottish champions, who have been fined 12 times by UEFA for the behaviour of their supporters in European competition in the last eight years, handed 1,000 of their 2,500 ticket allocation back.

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They stated after the match that followers of Hammarby, who are city rivals of AIK, had been sold briefs for their section and had been responsible for the ugly scenes which broke out. They also questioned the security arrangements inside the ground.

Local reports claimed that three Celtic fans had been arrested – one for throwing a firework at a steward, one for invading the pitch after the visitors had scored a goal and one for fighting.

But a Parkhead spokesman said: “Celtic were concerned that AIK sold to locals in their section. It was clear many Hammarby fans were in the Celtic sections and this was raised by Celtic officials before he match.

“A lot of Swedish fans managed to infiltrate the away section which we believe was a major factor in the issues which arose, there was a lack of control at the access points to the Celtic section.

"We are aware that a number of Swedish supporters entered the area for visiting fans and we are currently investigating events."

Neil Lennon’s side won the match 4-1 on the night and 6-1 on aggregate to secure a place in the Europa League draw in Monaco this afternoon.

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“I’m really proud of the team,” said Lennon. “I thought it was an outstanding team performance. To score four goals away in Europe against a champion team is no mean feat, but we looked very powerful.

“Some of our football was breathtaking going forward. The front four, particularly first half, were very exciting to watch. They look at real threat.

“Then we had good control of the second half. Scott Brown and Callum McGregor gave us that real platform and we defended resolutely when we needed to so it was a great all-round team performance and one that as a manager I didn’t envisage.

“I’m so proud of that and psychologically we’re in a good place. I’ve been saying for a while that we have the makings of a good team and we’ve gone out and shown that again tonight.”